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The FBI's shutdown at 12:01 AM Eastern Time Monday of servers supporting DNSChanger malware has not resulted in a huge outcry from Internet users worldwide.

Vikram Thakur, the principle security response manager at Symantec, told us that the impact of switching the replacement DNS servers off was "in line with what we expected."

"People with affected computers are less likely to publicize their network outage," Thakur said. "Instead, they'll be communicating with their local ISPs or computer technicians over the next several days or weeks."

According to the non-profit DNS Changer Working Group (DCWG), the malware works in tandem with DNS servers operated by cyber-criminals around the world. Given that all Web connections begin with DNS, DNSChanger makes it possible for criminals to deliver fake and malicious answers to search queries as well as direct the users of infected machines to fraudulent Web sites promoting bogus or even dangerous products.

"Efforts to spread the word about the effects of shutting down the DNSChanger servers have hopefully made an impact," Thakur said. However, Thakur also noted that DCWG's data indicates "there is still an estimated 260,000 computers that will be affected" by Monday's shutdown.

Prepping the DNS Server Shutdown

Last November, the FBI began operations against the cyber criminals running the rogue servers that support the DNSChanger malware. Since then, the bureau's cyber division has been working with the non-profit DCWG organization to operate temporary clean DNS servers.

The DCWG also established a Web site for hosting the detection tools that consumers needed to determine whether their machines are infected with a DNS changing virus such as TDSS, Alureon, TidServ or TDL4. The Web site provides consumers with infected machines with the directions for how to remove any of these viruses.

These preparatory steps helped pave the way for Monday's DNS server shutdown, according to the FBI.

"We've been using the last eight months to go out and clean up the infected computers, but we don't have everybody," said Thomas Grasso, a supervisory special agent at the FBI's cyber division.

Removing the Threat

Under the plan developed by the FBI and non-profit DNS Changer Working Group (DCWG), all the remaining infected PCs were to receive an "ICMP Unreachable" message beginning Monday morning. Thakur noted that Symantec's products do detect and remove the DNSChanger malware -- and non-Symantec customers can use Norton Power Erase to remove the threat -- but Symantec's security software cannot change the DNS configuration settings of infected machines.

"This is because there is no way for us to know the correct settings for each individual computer," Thakur said. "Users' ISPs should be able to walk them through correcting their settings. Alternatively, users can go to [the DCWG.org Web site] to see if they are affected by the issue and then follow the links describing how to correct their settings."

On the other hand, F-Secure reported Monday that some major Internet service providers appear to have configured their own substitute DNS servers that allow infected users on their systems to continue to access the Web -- even as these ISPs attempt to work out a final solution for the DNSChanger botnet problem.

"The FBI is out -- and ISPs are in," said F-Secure Security Labs blogger Mikko Hypponen. "All in all, things are working out as they probably should in a case such as this. The infection count continues to decrease without a major crisis in [ISP] support calls."